In the sentence 'Why do we pay taxes?', the sentence is asking about:

In the reading sentence 'Why do we pay taxes?', the question word 'Why' indicates the sentence is asking about a reason. The USCIS reading test combines question words, civics vocabulary (like 'taxes' and 'pay'), and verbs into short, readable sentences. Comprehending what the sentence asks — here, the reason for paying taxes — demonstrates the reading understanding the test measures. 'Why' always points to a reason or cause, just as 'Where' points to a place and 'When' to a time. Recognizing the sentence's meaning is part of the sentence-comprehension skill.